/*
  Copyright 2012 Stefano Chizzolini. http://www.pdfclown.org

  Contributors:
    * Stefano Chizzolini (original code developer, http://www.stefanochizzolini.it)

  This file should be part of the source code distribution of "PDF Clown library" (the
  Program): see the accompanying README files for more info.

  This Program is free software; you can redistribute it and/or modify it under the terms
  of the GNU Lesser General Public License as published by the Free Software Foundation;
  either version 3 of the License, or (at your option) any later version.

  This Program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY,
  either expressed or implied; without even the implied warranty of MERCHANTABILITY or
  FITNESS FOR A PARTICULAR PURPOSE. See the License for more details.

  You should have received a copy of the GNU Lesser General Public License along with this
  Program (see README files); if not, go to the GNU website (http://www.gnu.org/licenses/).

  Redistribution and use, with or without modification, are permitted provided that such
  redistributions retain the above copyright notice, license and disclaimer, along with
  this list of conditions.
*/

using org.pdfclown.documents;
using org.pdfclown.files;
using org.pdfclown.objects;

using System.Collections.Generic;

namespace org.pdfclown.tools
{
  /**
    <summary>Tool to enhance PDF files.</summary>
  */
  public sealed class Optimizer
  {
    #region types
    private class AliveObjectCollector
      : Visitor
    {
      private ISet<int> aliveObjectNumbers;

      public AliveObjectCollector(
        ISet<int> aliveObjectNumbers
        )
      {this.aliveObjectNumbers = aliveObjectNumbers;}

      public override PdfObject Visit(
        PdfReference obj,
        object data
        )
      {
        int objectNumber = obj.Reference.ObjectNumber;
        if(aliveObjectNumbers.Contains(objectNumber))
          return obj;

        aliveObjectNumbers.Add(objectNumber);
        return base.Visit(obj, data);
      }
    }
    #endregion

    #region static
    #region interface
    #region public
    /**
      <summary>Removes indirect objects which have no reference in the document structure.</summary>
      <param name="file">File to optimize.</param>
    */
    public static void RemoveOrphanedObjects(
      File file
      )
    {
      // 1. Collecting alive indirect objects...
      ISet<int> aliveObjectNumbers = new HashSet<int>();
      {
        // Alive indirect objects collector.
        IVisitor visitor = new AliveObjectCollector(aliveObjectNumbers);
        // Walk through the document structure to collect alive indirect objects!
        file.Trailer.Accept(visitor, null);
      }

      // 2. Removing orphaned indirect objects...
      IndirectObjects indirectObjects = file.IndirectObjects;
      for(int objectNumber = 0, objectCount = indirectObjects.Count; objectNumber < objectCount; objectNumber++)
      {
        if(!aliveObjectNumbers.Contains(objectNumber))
        {indirectObjects.RemoveAt(objectNumber);}
      }
    }
    #endregion
    #endregion
    #endregion
  }
}
